Dr. Roach: Can a low oxalate diet improve blood pressure?

Keith Roach
To Your Health

Dear Dr. Roach: My blood pressure crept up on me, and I went on medication. I had been eating what I thought was a healthy diet to keep my blood pressure in check. My nutritionist suggested to me I back off my handful of almonds daily and check my intake of other foods high in oxalates. Two weeks later, my blood pressure was normal. I stopped taking blood pressure medication, and after four years, my pressure has stayed low-to-normal.

— D.

Dear D.: Oxalate is a plant-derived chemical present in many foods — such as almonds, but also dark leafy greens such as chard and spinach. A low oxalate diet is often recommended in people with a history of calcium oxalate stones. I could not find definitive proof that oxalates increase blood pressure in people with no history of kidney stones.

A large trial looking at oxalate intake in people with chronic kidney disease showed that those with large amount of oxalate intake had a greater risk of progressing to worse kidney disease, but there was no difference in blood pressure among the different groups. Individual trials showed that some high oxalate foods, such as beetroot juice and green tea, lowered blood pressure in healthy volunteers.

Dr. Keith Roach

The DASH diet — which is high in fruits, vegetables, legumes and nuts, moderate in low-fat dairy products, and low in animal proteins, refined grains and sweets — has been shown to reduce blood pressure. This is not a low oxalate diet, but was compared against a low oxalate diet in people with a history of kidney stones. In the study, those who followed the DASH diet reduced their risk of kidney stones to a greater extent than those who consumed a low oxalate diet, suggesting the dietary effect of oxalate is small.

I’m glad your diet helped you, but since many foods high in oxalate are healthy for other reasons, I wouldn’t recommend a low oxalate diet without a good reason (like stones) or other evidence of benefit, which I don’t find.

Dear Dr. Roach: At my yearly physical exam, my creatinine was 1.11 (normal range 0.6-0.88). What do I need to do? Is it safe to use Tylenol?

— C.C.

Dear C.C.: The higher the creatinine number, the worse the kidney function. However, if you hadn’t eaten or drunk any fluids for a long time before your lab test, that could have made the creatinine go up too. The overall pattern of your creatinine over time needs to be considered. A fast increase is much more concerning than a stable or slowly increasing level.

Most often, in people with a modest elevation in creatinine, nothing needs to be done beyond making sure you aren’t hurting your kidneys. Anti-inflammatories like ibuprofen and naproxen are much more dangerous to your kidneys than Tylenol, which is safe if taken occasionally. However, even Tylenol taken at high doses over many years can itself cause kidney damage. A kidney specialist is the expert who should be consulted if your creatinine keeps going up.

Dr. Roach writes: A recent column on RhD incompatibility and hemolytic disease of the newborn contained an embarrassing typo: It’s when the mother is RhD negative and the father is RhD positive that the danger lies, and I wrote it backward. Most people were relatively nice about pointing out this error.

Readers may email questions to ToYourGoodHealth@med.cornell.edu.